SummaryThe clinical, biochemical and pathological findings in a family with four cases of metachromatic leucodystrophy are presented. The biochemical studies of one of the cases revealed the absence of urinary sulphatase A and the preponderance of two glycolipid fractions in urinary sediment.The patient in question was fed a diet low in vitamin A for four months. This diet reduced the relative amount of glycolipids five times in the urinary sediment (relative to the total content of sialic acid free polar lipids). The diet did not change the sulphatase activity. However, no significant clinical improvement of the patient was noticed. The biochemical changes induced by the deficiency in vitamin A are discussed on the basis of biochemical studies showing vitamin‐A to be necessary for the synthesis of active sulphate (PAPS). PAPS is necessary for sulphate incorporation in galactoceramide during biosynthesis of sulphatide. It is suggested that a diet deficient in vitamin A may be used in treatment of metachromatic leucodystroph